edu.northwestern.at.utils.math
Class Factorial

java.lang.Object
  edu.northwestern.at.utils.math.Factorial

public class Factorial
extends java.lang.Object

Defines methods for factorials.

Field Summary

protected static double[]	doubleFactorials
protected static long[]	longFactorials

Constructor Summary

Factorial()

Method Summary

static double	factorial(int n) Compute factorial of an integer.
static double	logFactorial(int n) Computes the natural log of n factorial.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

longFactorials

protected static final long[] longFactorials

doubleFactorials

protected static final double[] doubleFactorials

Constructor Detail

Factorial

public Factorial()

Method Detail

factorial

public static double factorial(int n)

Compute factorial of an integer.

Parameters:

n - Number for which to compute factorial.

Returns:

n!

logFactorial

public static double logFactorial(int n)

Computes the natural log of n factorial.

Parameters:

n - The number for which the log factorial is desired.

Returns:

The natural log of n! .

We use the LogGamma function to compute log(n!) using the relation:

log(n!) = logGamma( n + 1 )